Measurement of 400,000 galaxies will allow a precise measurement of the clustering of matter on different scales in the Universe and ought to reveal the “baryon wiggles”, a relic feature from the primordial Big Bang. This encodes a fundamental physical scale whose size we can measure from the cosmic microwave background.

Measuring this “standard ruler” at z=0.75 will give us the first high-precision measurement of “dark energy” independent of previous supernovae determinations.